This invention relates to an article with a substrate or film adjacent a formed base material.
In a typical in-mold decorating process (IMD), a printed substrate is formed into a three-dimensional shape and placed into a mold. Molten resin is then injected into the mold cavity space behind the formed substrate to form a single molded part.
IMD may involve two types of film processes. According to one process, the film is a permanent fixture of the finished good. In this case, the film may act as the aesthetic effect carrier, or as a protective layer for the base resin, aesthetic effect, or both. Good adhesion is desired between the film, such as a polycarbonate type film, and the base resin.
According to another process, the film may be a temporary carrier for the aesthetic effect. In this case a base resin may be back-molded to the IMD film. The film is subsequently peeled off of the base resin, transferring or leaving an aesthetic material or design on the substrate resin. Good adhesion is not desired between the film, which may be a poly (ethylene terephthalate) type film and the substrate resin.
For both types of in-mold decorating (IMD) applications, ink washout of the IMD film is an inherent problem. When an ink (or other aesthetic enhancement) bearing or containing film is back-molded by a base resin, the aesthetic ink or effect material is often sandwiched between the IMD film and the substrate resin. The resulting shear from the back-molding injection of the substrate resin material against the IMD film, coupled with the heat of the molten substrate resin may cause the ink (or aesthetic bearing material) to detach itself from the IMD film. As a result, an area of decreased ink concentration, or xe2x80x9cwashoutxe2x80x9d may form. This washout is caused by several processing factors of the substrate resin, including processing temperature and injection shear.
Other challenges during the IMD process sheet or foil breakage or wrinkling which may be a result of the high pressures and temperatures needed to back mold.
A resin used as an IMD base material is a blend of polycarbonate (PC) with ABS (acrylonitrile-butadiene-styrene), such as a CYCOLY(copyright) resin produced by GE Plastics. PC/ABS blends have typically have enhanced shear thinning which enables the molder to fill the mold at lower injection rates and temperatures.
U.S. Pat. No. 3,654,062 to Loew describes a molded decorative plaque having a laminated facing sheet, which has the configuration of the mold. Heated plastic is injection molded behind the sheet to form the plaque. U.S. Pat. No. 6,117,384 to Laurin et al. describes a process where colors are decorated into a single film, which is then incorporated with a molten resin injected behind the film to produce a permanently bonded three-dimensional piece. U.S. Pat. No. 4,391,954 to Scott describes a thermoplastic molding composition comprising an aromatic carbonate polymer and a polyester derived from a cyclohexanedimethanol. U.S. Pat. No. 4,125,572 to Scott describes a thermoplastic molding composition comprising an aromatic carbonate polymer and a polyester derived from an aliphatic or cycloaliphatic diol. U.S. Pat. No. 4,662,966 to Nissha Printing Co. Ltd. describes a transfer-printing machine where designs of a diffusible dye on a transfer sheet are transferred to heated articles.
For the base material, it is desired to have a high clarity material with improved chemical resistance and with low temperature impact. The chemical resistance of many transparent and translucent amorphous materials is not sufficient against chemicals like oleic acid or sun tanning lotions, which are considered to be important chemicals in qualifying new materials for molding applications in for use in telecom and electronics businesses.
A molded structure comprises a decorative surface area with an integrally formed polymeric base which comprises a substantially transparent or translucent cycloaliphatic polyester resin. In one embodiment, the decorative area is integral with or forms a part of an adjacent formed substrate. The decorative surface may be formed directly on the surface of the polymeric base such as by a transfer process. In another embodiment, the decorative surface comprises a film or other substrate, which is back molded with the transparent cycloaliphatic polyester resin. In this embodiment, the substrate may have at least one opening which exposes the transparent polymeric base resin to the exterior of the molded article.
According to a molding method embodiment, a printed substrate is formed into a three-dimensional shape and placed into a mold. Molten resin is then injected into the mold cavity space behind the formed substrate, forming a single molded part.
The use of a transparent cycloaliphatic polyester resin as the injection molded base material obviates disadvantages encountered with non-transparent PC/ABS type blends. Lack of transparency may be a significant drawback in certain applications. For instance, for some cell phones, a film (PET) with ink patterns is back molded with a transparent resin to mold the complete front cover. This is done so that information can be visually accessed by the product""s user through an opening positioned in the film or sheet, which is integrated into the structural resin of the product""s design so as to form a transparent window. During back molding, the injection molded material projects into an opening in the film to form the window.
According to another process, during the back molding, ink may be transferred from a film to the transparent base resin. Removal of the film, dye or ink is transferred to the base material resulting in a decorated front cover. An example of transfer printing is the Nissha process. See U.S. Pat. No. 4,662,966 to Sumi et al. According to the process set forth, articles to be transferred-printed are heated such as by infrared radiation. A transfer sheet having an image or aesthetic effect formed thereon with a diffusible dye is pressed against the surface of the articles so that the aesthetic effect is transferred to the surfaces of the heated articles. The transfer sheet is then removed. According to one embodiment, the article, which may be pressed against the transfer sheet by back molding or the application of pressure, may be a transparent cycloaliphatic polyester resin. According to another embodiment, the transfer sheet, which carries the diffusible dye, may comprise a cycloaliphatic polyester resin.
For some applications, the film of substrate material may be a permanent aesthetic part of the finished product. For some wireless personal electronic applications which may use a film such as a polycarbonate (PC) film with ink patterns which is back molded with a transparent resin to mold the complete product housing. The transparent base material is molded to create a transparent window. Data may be transferred to/from the electronic product to its server by IR through the transparent window which is integrated into the structural resin of the product. Holes in the film expose the transparent injected molded base resin for either data transfer or aesthetic purposes.
One possibility for a transparent material is polycarbonate (PC). Typically, the processing temperature and injection shear (viscosity) of PC results in washout of ink on the IMD film at the injection gate. Other higher flow transparent materials like LEXAN(copyright) SP resin, a super high flow PC grade produced by GE Plastics component of General Electric Company give an improvement in terms of viscosity, but have a very small processing window and as such are not very robust. Even these higher flow materials are not suitable for thinner-walled IMD parts where their fast injection speeds will still result in IMD washout and other issues as described above (e.g. foil breakage). In addition, physical properties, especially impact of LEXAN SP resin and other such high-flow products are also not sufficient for use in many IMD applications.
Cycloaliphatic polyester and polycarbonate blends, with or without an impact modifier are utilized as a back-molded resin for in-mold decorated (IMD) film applications. Transparent blends of polycarbonate (PC) and poly(cyclohexane dimethanol cyclohexane dicarboxylate) (PCCD) which posses lower processing temperatures and improved flow characteristics over standard PC materials. This results in slower injection speeds and lower injection shear in an injection molded IMD part when compared to other transparent back-molding substrate resins (such as Lexan SP) for in-mold decorating (IMD) applications. This in turn results in a decrease of the washout effect in IMD applications. These blends also offer superior chemical resistance and ductility to that of most transparent resin materials. The complete miscibility of this system allows the properties of the resulting blend to be dialed in, via blend ratio, while still maintaining transparency.
Two types of cycloaliphatic polyesters may desirable can be used with BPA-based polycarbonate to give the compositions and articles of this invention. The most preferred polyester molecules are derived from cycloaliphatic diol and cycloaliphatic diacid compounds, specifically polycyclohexane dimethanol cyclohexyl dicarboxylate (PCCD). The polyester having only one cyclic unit may also be useful.
In addition, PCCD and PC can be blended with certain impact modifiers (IM) at such ratios as to match the refractive index (RI) of the impact modifier to that of the PC/PCCD blend and therefore still retain transparency. In addition to the characteristics of PC/PCCD resins, these PC/PCCD/IM blends possess improved low temperature ductility which can be a key requirements for IMD applications, for example, cellphone covers.
The present invention is directed to multi-layer plastic articles and methods for making such articles. More particularly, the articles comprise a base layer of an injection molded thermoplastic and surface layer of a decorated film or a transferred aestheticly decorative surface.
The desired multi-layered films have favorable properties of formability, low birefringence, chemical, UV radiation resistance, and optical transparency. These laminated films are well suited for exterior automotive insert mold decoration (IMD) applications. According to an IMD process, a formed, and decorated film is placed in a mold and the thermoplastic melt, which forms the base layer, is injection molded to the exposed surface of the film.